Elevator system including multiple cars in a hoistway

ABSTRACT

An elevator system ( 20 ) includes multiple cars ( 22, 24 ) within a hoistway ( 40 ). Parking positions ( 72, 74 ) are provided outside the range of passenger service levels ( 70 ). A destination entry strategy is used by a controller ( 60 ) for directing movement of the elevator cars ( 22, 24 ). The inventive combination of multiple cars in a hoistway, parking positions outside of the normal passenger service level range and destination entry car movement control allows for reducing car travel speed, reducing car size or both while still meeting desired handling capacity needs or even exceeding the desired handling capacity associated with another elevator system that requires larger cars, higher speeds and more building space.

FIELD OF THE INVENTION

This invention generally relates to elevator systems. More particularly,this invention relates to an elevator system including multiple carswithin a single hoistway.

DESCRIPTION OF THE RELATED ART

Elevator systems typically include an elevator car that travels througha hoistway between different levels within a building. While somebuilding sizes are small enough to accommodate a hydraulic elevatorarrangement, most larger buildings require a car and counterweightarrangement. For larger buildings, there have been efforts at arrangingan elevator system to maximize customer service and to enhance passengertraffic flow. Conventional thinking has suggested using larger cars andhigher speeds for carrying more passengers more quickly. Other proposalsalso have been made because there are practical limits on car size andspeeds.

One technique is to use channeling or sectoring where an elevator car isassigned to service a particular grouping of floors within a building,for example. While sectoring provides increased handling capacityespecially during up peak or down peak periods, there is the drawbackthat individualized passenger service may be compromised. For example,the time between a passenger making an elevator call and arriving at adesired destination may be longer with some sectoring arrangements undersome circumstances when compared to other elevator system arrangements.

Another known technique is referred to as destination entry. With thistechnique, an individual provides an indication of their intendeddestination before entering an elevator car. This is different thanconventional arrangements where a button on a car operating panel withina car allows a passenger to choose a destination floor, for example.Destination entry systems often have a main lobby device wherepassengers indicate their intended destinations. The elevator systemuses such destination indications for assigning passengers to particularcars.

One advantage of destination entry systems is that individualizedpassenger service may be enhanced. The wait time between entering anintended destination and arriving at that destination can be reducedwith many destination entry systems. Destination entry systems, however,typically do not accommodate up peak and down peak travel times in anefficient manner.

Another proposed enhancement to elevator systems for increasing handlingcapacity has been to incorporate more than one elevator car within ahoistway. This is shown for example in U.S. Pat. No. 1,837,643 and thepublished United States Patent Application No. US 2003/0075388. Sucharrangements tend to be beneficial for inter-floor traffic and theyrequire less building space while providing the same handling capacityof elevator systems having a single car within each hoistway. Onedisadvantage to such arrangements is that they typically are notwell-suited for up peak and heavy two-way traffic situations.Additionally, there is no substantial cost reduction associated withsuch a system when compared to a traditional, single-car-per-hoistwayarrangement.

One other proposed arrangement is shown in U.S. Pat. No. 5,419,414. Thatdocument discloses an arrangement where parking areas are provided aboveand below the normal range of elevator car operation. The parking areasfacilitate using more than one car in a hoistway and allowing each carto service all possible floors.

While each of the above-described proposals present an opportunity forenhancing elevator system operation, there is still a need for betterperformance and lower cost systems. This invention includes acombination of elevator system-enhancing features that provides for alower cost system that does not compromise handling capacity or systemperformance. The inventive combination of features provides anunexpected result that yields enhanced elevator system performance at alower cost compared to previously proposed systems.

SUMMARY OF THE INVENTION

An exemplary disclosed elevator system includes a plurality of cars withat least two of the cars supported for movement within a singlehoistway. A controller receives an intended passenger destinationindication before a corresponding passenger enters one of the cars. Thecontroller assigns at least one of the cars to travel according to thereceived destination indication. The controller selectively directs atleast one of the two cars to a parking position outside of the range ofthe passenger service levels. In one example, the parking positions areat least one of beneath a lowest passenger service level or above ahighest passenger service level.

In one example, the parking areas are utilized during up peak or downpeak travel times. In one example, the controller selectively directs afirst one of the two cars to the parking position above the highestpassenger service level and the other of the two cars to the parkingposition below the lowest passenger service level.

An example method of designing an elevator system includes determining adesired handling capacity. Determining a traditional system design toachieve the desired handling capacity includes determining the typicalnumber of cars, typical duty load of each of the cars and a typicaltravel speed of the cars. Selecting a number of cars and selecting atleast one of a duty load that is less than the typical duty load or atravel speed that is lower than the typical travel speed still achievesthe desired handling capacity in an elevator system designed accordingto this invention. In one example, the duty load and the travel speedare selected to be less than the corresponding typical parameters.

In one example, selecting more cars than a typical number andincorporating more than one car per hoistway allows for reducing theamount of building space required to accommodate the elevator systemwhile still achieving the desired handling capacity.

The various features and advantages of this invention will becomeapparent to those skilled in the art from the following detaileddescription of currently preferred embodiments. The drawings thataccompany the detailed description can be briefly described as follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates an elevator system designed accordingto one embodiment of this invention.

FIG. 2 graphically illustrates a relationship between elevator systemparameters and handling capacity as used in an example method ofdesigning an elevator system such as the example of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 schematically shows an elevator system 20. A plurality ofelevator cars 22-36 are arranged within a plurality of hoistways suchthat there are at least two cars in each of the example hoistways. Ascan be appreciated from the figure, the elevator cars 22 and 24 aresupported for movement within a first hoistway 40. The elevator cars 26and 28 are supported for movement within a hoistway 42. Similarly, thecars 30 and 32 are supported within a hoistway 44 while the cars 34 and36 are supported within a hoistway 46.

Elevator machines 50-56 are associated with the respective hoistways forcausing desired movement of at least one selected car. In one example, aseparate machine is dedicated to each car. The machines 50, 52, 54 and56 operate responsive to control signals from a controller 60. In thisexample, the controller 60 operates to provide a destination entryfeature where passengers provide a desired destination indication usingan input device 62 that is located outside of the elevator cars.Designation entry systems are known and the example arrangement includesknown techniques for providing appropriate control signals from theinput device 62 to the controller 60 and ultimately for operating themachines 50-56.

The example arrangement includes display portions 64 and 66 to providepassengers with instructions for using the device 62, for example, andfor providing an indication of which car will carry the passenger totheir intended destination. A plurality of input buttons 68 in theillustrated example operate in a manner similar to a floor selectionbutton on a car operating panel, which is familiar to most elevatorpassengers.

The example system 20 provides elevator service to passengers at aplurality of service levels 70. In this example, the service levelsextend between a lobby level and a top floor level of the building inwhich the elevator system 20 is installed. The example arrangement alsoincludes parking positions that are outside of the range of servicelevels 70 for the elevator system. The hoistway 40, for example,includes a parking position 72 beneath the lowest passenger servicelevel and a parking position 74 above the highest passenger servicelevel. The hoistway 42 includes parking positions 76 and 78 while thehoistway 44 includes parking positions 80 and 82. The hoistway 46similarly includes a parking position 84 beneath the lowest passengerservice level and a parking position 86 above the highest passengerservice level. In the illustrated example, the parking positionsaccommodate a single elevator car. In another example, more than one carmay be parked within a parking position under selected circumstances.

The controller 60 directs at least one of the cars to an appropriateparking position to accommodate elevator traffic requirements during uppeak or down peak periods, for example. Allowing cars to go into theparking positions provides for the ability of every car within ahoistway to provide service to every floor at which passenger service isavailable for that hoistway. In one example, the controller 60 does notalways direct a car to a corresponding parking position, but only whenpassenger traffic conditions indicate that to be advantageous. In thatsense, the controller 60 selectively directs at least one of the cars toan appropriate parking position on an as-needed basis.

In the illustrated example, the machines 50, 52, 54 and 56 are supportedwithin the upper parking positions 74, 78, 82 and 86, respectively. Inother words, the illustrated arrangement is a machine roomless elevatorsystem where a separate machine room is not required. In this example,the parking positions above the highest passenger service level occupythe space that would have been occupied by a machine room in anotherarrangement.

No one has previously combined using multiple cars within a hoistway, adestination entry strategy and parking positions for elevator carsoutside of the range of the normal passenger service levels. Thiscombination provides significant advantages compared to previous systemsand an unexpected result. With this combination, optimum performance isprovided for all traffic conditions including up peak and down peaktravel times. Additionally, there is a significant space savings becauseless hoistways are required compared to arrangements where a single caris supported within each hoistway. Moreover, the inventive combinationallows for significant cost savings.

One unexpected result associated with this invention is that thecombination of multiple cars in a hoistway, parking positions outside ofthe normal passenger service level range and destination entry carcontrol allows for actually reducing the travel speed of the cars, theduty load and size of the cars or both while still providing the samehandling capacity or even enhanced handling capacity at a lower cost.This is directly contrary to conventional thinking, which suggests usinglarger cars and faster speeds as a means of maximizing handlingcapacity.

Utilizing slower speeds for the cars while still maintaining a desiredhandling capacity allows for cost savings because, in part, it allowsfor using smaller elevator machines (i.e., motors), which allows forless expensive components. Additionally, lower elevator speeds make iteasier to maintain ride comfort in many situations. This allows for aless-complicated system design. Additionally, the smaller components anda more straight-forward system design reduces complexity forinstallation, which reduces labor time and installation expenses.

Reducing the size or duty load of the cars allows for using smaller carsand correspondingly smaller counterweights, which introduces materialsavings. Moreover, using smaller cars allows for utilizing smallerhoistways, which present a substantial savings in the amount of buildingspace required for achieving a desired handling capacity. The examplesystem 20 only requires four hoistways compared to a traditional systemthat would require at least six hoistways (each accommodating one car)for achieving the same handling capacity. Additionally, the fourhoistways of the example system 20 can be smaller so that even lessbuilding space is required. Reducing the amount of building spaceoccupied by an elevator system is considered an important feature tobuilding owners where maximizing rental space results in maximizing thebuilding owner's profitability associated with a particular building.

FIG. 2 graphically shows the relationship between an elevator systemhandling capacity and different elevator system parameters. A graphicalplot 100 shows system handling capacity versus elevator system designparameters. The plots shown in the graphical illustration 100 are basedupon the known up peak handling capacity formula that can be expressedas UPPHC=(300*duty*0.8*number of cars)/((2*ave.HF*T1 floortransit)+((ave.stops+1)*(Tperformance−T1 floortransit))+(2*duty*0.8*(Tload+0.5*Tunload))); where duty represents theduty load of the cars, ave.HF is the average highest floor reached, T1floor transit is the single floor flight time, ave.stops is the averagenumber of stops made, Tperformance is the performance time, Tload is theloading time and Tunload is the unloading time.

Based upon this relationship, it can be determined that the handlingcapacity of an elevator system is primarily dependent upon the number ofcars. This realization is new and contrary to the conventional thinkingthat larger cars and faster speeds provide more handling capacity.

In FIG. 2 where a 13% handling capacity is shown at 102. A traditionalsystem design using the above formula yields a typical number of cars, atypical duty load for each car and a typical car speed to achieve thedesired handling capacity. These values all coincide at 102.

A first plot 104 represents how changing the speed of the cars changesthe handling capacity of the elevator system. As can be appreciated,varying the speed by 75% in a positive or negative direction does nothave a substantial impact on the handling capacity of the system.

The plot 126 shows how varying the duty load (i.e., size of the car) hasan impact on the handling capacity. While changing the duty load has amore significant impact than changing the car speed, the change with a75% variation in the duty load in either direction corresponds to achange of only about 5% in the handling capacity.

The plot 108 represents the effect of the number of cars in the systemon the handling capacity. The most dramatic changes in handling capacityoccur when changing the number of cars. By decreasing the number ofcars, for example, from the point shown at 102, the handling capacitydrops more significantly than when decreasing the speed or duty load ofthe cars. When increasing the number or cars from the point shown at102, the handling capacity can be substantially increased, especiallycompared to a similar change in the percentage of the car speed or dutyload.

One feature of a method of designing an elevator system in oneembodiment of this invention includes selecting at least one of a lowercar travel speed or a smaller car size (i.e., lower duty ratio) comparedto that which would be used in a more traditional system design to meeta particular handling capacity. In other words, one example approach fordesigning an elevator system begins with determining a desired handlingcapacity. Determining the number of cars, duty load and car travel speedrequired to achieve that handling capacity using a traditional elevatorsystem design provides a baseline for then selecting system parametersto be consistent with an embodiment of this invention to achieve thesame or better handling capacity in a more efficient manner. In oneexample, selecting a lower car speed than that which would be requiredin the typical system design provides cost savings as described above.In another example, selecting a smaller car size provides the advantagesdescribed above. In still another example, lower travel speed andsmaller car size are combined to provide further savings andenhancement.

Increasing the number of cars overrides the effects of reducing travelspeed or car size because of the more profound impact on handlingcapacity associated with the number of cars. Using destination entrycontrol and incorporating multiple cars in a hoistway with parkingpositions so that each car can service most or all passenger servicelevels associated with a particular hoistway allows for reducing the cartravel speed, the car duty load or both and provides a significantlyenhanced elevator system performance at a lower cost.

The preceding description is exemplary rather than limiting in nature.Variations and modifications to the disclosed examples may becomeapparent to those skilled in the art that do not necessarily depart fromthe essence of this invention. The scope of legal protection given tothis invention can only be determined by studying the following claims.

1. An elevator system, comprising: a plurality of cars, at least two ofthe cars supported for movement within a single hoistway; and acontroller that receives an intended passenger destination indicationbefore a corresponding passenger enters one of the cars, assigns atleast one of the cars to travel according to the received destinationindication, and selectively directs at least one of the two cars to aparking position that is at least one of beneath a lowest passengerservice level or above a highest passenger service level.
 2. The systemof claim 1, including at least two cars in each of a plurality ofhoistways.
 3. The system of claim 1, wherein the lowest passengerservice level is a lobby level.
 4. The system of claim 1, wherein thecontroller selectively directs one of the two cars to the parkingposition beneath the lowest passenger service level and the other of thetwo cars to the parking position above the highest passenger servicelevel.
 5. A method of controlling an elevator system, comprising:providing a plurality of cars with at least two of the cars supportedfor movement in a single hoistway; receiving an intended passengerdestination indication at a location outside of the cars; assigning atleast one of the cars to travel according to the received destinationindication; and directing at least one of the two cars to a parkingposition that is at least one of beneath a lowest passenger servicelevel or above a highest passenger service level.
 6. The method of claim5, including directing the car to the parking position during at leastone of an up-peak or a down-peak passenger travel period.
 7. The methodof claim 5, including selectively directing one of the two cars to theparking position beneath the lowest passenger service level and theother of the two cars to the parking position above the highestpassenger service level.
 8. A method of designing an elevator system,comprising: determining a desired handling capacity; determining abaseline system design to achieve the desired handling capacity thatincludes a typical number of cars, a typical duty load of each of thecars and a typical travel speed of the cars; and selecting a number ofcars and selecting at least one of a duty load for the selected numberof cars that is less than the typical duty load, or a travel speed thatis lower than the typical travel speed, to thereby achieve the desiredhandling capacity.
 9. The method of claim 8, including selecting anumber of cars that is greater than the typical number.
 10. The methodof claim 9, including selecting the duty load to be less than thetypical duty load and selecting the travel speed to be lower than thetypical travel speed.
 11. The method of claim 9, including providing aplurality of cars within a single hoistway.
 12. The method of claim 11,including providing parking positions at least one of above or below arange of passenger service levels.
 13. The method of claim 11, whereinthe baseline system design includes a typical building space required toaccommodate an associated number of typical hoistways within which thecars move and the method includes utilizing less building space than thetypical building space.
 14. The method of claim 8, including selectingthe duty load to be less than the typical duty load and selecting thetravel speed to be lower than the typical travel speed.